This protocol is designed to evaluate the repeat administration of a replication deficient, recombinant adenovirus vector and its ability to transfer the normal human cystic fibrosis transmembrane conductance regulator cDNA to the respiratory epithelium of individuals with cystic fibrosis. Study individuals will undergo a series of studies at designated intervals to evaluate safety and efficacy of this therapy. These tests include: general assessment, blood and urine analysis, EKG, chest x-ray, lung function tests, sputum culture, and bronchoscopy. At completion of the study, the following questions will be answered: (1) Is it safe to repeatedly administer a vector in this fashion to individuals with CF?; (2) Will the vector transfer the normal cDNA such that it is expressed in the airway epithelium and will it correct the biologic abnormalities; (3) Is there improvement in clinical signs and symptoms relevant to CF?; and (4) Does this therapy evoke humoral immunity?